1. Field of the Invention
The present invention relates to a module test apparatus. Particularly, this invention relates to a socket type module test apparatus including a transportation unit which automatically loads and unloads modules for testing and provides stable mechanical and electrical contact between modules and test sockets during test. This invention also relates to a socket used for the module test apparatus.
2. Description of the Related Arts
A number of semiconductor devices are often combined on a single substrate and used as a module to improve the performance of the system that uses the semiconductor devices. For example, memory integrated circuit chips mounted on a printed circuit board form a memory module. A module generally comprises a number of semiconductor devices and a substrate. The semiconductor devices are mounted on one side or both sides of the substrate and are electrically interconnected by wiring patterns formed in the substrate. The substrate typically contains a number of external terminals extending from the wiring patterns along an edge of the substrate.
Modules are tested to verify their characteristics. Two types of module tests are generally used. One is a manual test where a module is manually loaded to and unloaded from a socket. The other is an automatic test which uses an automatic module handling unit and test pins.
In the manual test, an operator inserts modules by hand into sockets that are connected to a control unit and tests the modules by using the control unit. The control unit generates test signals, sends the signals to the modules, and evaluates the characteristics of the modules. After finishing the test, the operator removes the modules and classifies the modules according to the test results. This manual test method offers a stable contact mechanism between sockets and external terminals of modules. However, the manual test method also has several disadvantages. Among them are low test productivity due to the manual handling and the risk of human error in classifying the modules.
In contrast, the automatic test method increases module test productivity and reduces the possibility of human error. In this method, test signals are transferred to modules via test pins, so-called Pogo pins, not via a socket. An automatic module tester comprises a pin block which is somewhat similar to a socket, and the pin block has a number of test pins installed at positions where the pins contact external terminals of modules. Automatic testers use a test pin block instead of a socket because the test pin block allows easy and no-force insertion of modules, whereas the socket requires external force for insertion of modules.
A module tester using test pins will be described with reference to FIGS. 1 to 5. Test pin type module tester 100 comprises a main control unit 90, a test unit 10, and a transportation unit 20. Tester 100 further comprises a supply tray 32 which contains modules to be tested, an output tray 34 which collects the modules that passed a module test, and a collection bin 36 which collects modules that failed to pass the test.
Main control unit 90 controls test unit 10 and transportation unit 20. Main control unit 90 tests module 40 by generating and sending test signals to module 40 through test pins 14 which contact external terminals 41, judges whether module 40 passed the test, and does the loading and unloading of module 40 at pin block 12 by using transportation unit 20 (FIG. 2). In FIG. 1, reference numeral 92 refers to transmission lines through which signals are transmitted from main control unit 90 to test unit 10 and transportation unit 20.
Test unit 10 comprises a base block 16 which is composed of two pin blocks 12 which have plural test pins 14 for contacting external terminals 41 of module 40. As depicted in FIG. 4, which is a sectional view taken along the line 4--4 in FIG. 3, a test pin 14 is composed of a contact pin 19, a spring 17 and a sheath 13, and thereby, contact pin 19 can move elastically in and out of sheath 13. A tip 19a of contact pin 19 which contacts external terminal 41 of module 40 is embossed for good contact.
Referring to FIGS. 1, 2, and 5, transportation unit 20 comprises a loading picker 24 for transporting the modules to be tested from supply tray 32 to pin blocks 12, and a unloading picker 26 for transporting the tested modules from pin blocks 12 to output tray 34 or collection bin 36.
The test procedure using module tester 100 will be explained referring to FIGS. 1 to 5. First, loading picker 24 picks up module 40 in supply tray 32 and transports module 40 to a position above pin block 12 (FIG. 2). Then, loading picker 24 moves downward and places module 40 between pin blocks 12, pin blocks 12 move toward each other so that test pins 14 contact external terminals 41 of module 40, and the test is carried out (FIGS. 3 and 4). After the test is finished, unloading picker 26 picks up tested module 40, and pin blocks 12 return to their original positions to release module 40 (FIG. 5). Thereafter, unloading picker 26 goes up and transports tested module 40 to output tray 34, or to collection bin 36.
The automatic test using test pin type module tester can accomplish higher test productivity than the manual test. However, a contact to external terminals of module by test pin is less stable than the contact by socket, and the unstable contact may produce noise during test. That is, the unstable contact during test may produce incorrect test results. In addition, while the lifetime of a socket is about five hundred thousand tests, the lifetime of a test pin is about fifty thousand tests.
Therefore, a module test apparatus is required to accomplish high test productivity, stable contact to module, and low maintenance cost.